Separable drill bit



Aug. 25, 1936.

,L B. BAKER sEPARABLE-DRILL BIT Filed Dec. 26, 1951 Patented Aug. 25,5.11936.)

. UNijr'En s SEPARABLE BREIL BIKE' John B. Baker, Canton, Ohio, assignerto The Timken Roller Bearing Company, Canton, f 0hio,-a corporation ci(Ehio Application December 26, 1931, Serial No. 583,256

2 Claims.

separable drill bit and inthe parts and combinations and arrangements ofparts hereinafter described and claimed. e

In the accompanying drawing,

Fig. 1 is an elevation of a drill rod and separable bit provided withthreaded portions embodying my invention, the bit being shown insection,

' Fig. 2` is a similar view showing the parts separated.

Fig. 3 is an enlarged diagrammatic view showing the thread contours,

Figs. 4 and 5 are views similar to Figs. 1 and 3 of a modiiled threadconstruction, and

Fig. 6A is a view similar tojEig.v 1 showing a washer at the end ofthedrill rod.

Great diiliculty has been found in making.

threaded -bits `which will not bind upon the threaded end of the drillrod. Various thread..

structures have been devised, such as a. thread having a substantiallycontinuous curved contour. In all previous constructions, however,repeated impact tends to flat-ten out portions of the sides of thethreads and pack `the metal into tane spaces at the crest and hollows ofthe threads, thereby causing the parts to become tightly jammed togetherand frequently causing the parts to break.

According to my invention,I the tendency for the middleportions of thethreads to become attened is obviated and the parts continue to beVseparable under the most severe usage.

The drawing illustrates the `usual hexagonal drill rod l having athreaded end A cooperating with 'the threads B .of an interiorlythreaded vbit member 2. The threads A and B have a generally curvingcontour.' One thread, illustrated 'as being the thread A of the drillrod has the-crest 3 thereof provided with a rakiius'of curvature R. thatis greater than the radius of curvature R.' of the base portion. Thus,the crest 3 of the thread A of the drill rod is wide and at ascomparedwith the,. curve of the base portion of the thread and as compared withthe trough 4 between the base portions oi' the threads A. The crest 5-of the other thread B has a shorter radius of curva.-v

. portions of said threads being different from the" 'ing to the spacebetween threads of the other portionof the thread of said drill rodbeing' greater than the radius of curvature ofthe inner portion (CH.Z55-64) ture r than that 1'" of thread B.'

Both threads A and B are provided with dattened bands 6 along theirsides. The width of these iiattened bands or zones 6 is preferablir a 5little less. than one-third. of the linear surface distance from thecenter of the crest of the thread tothe center of the trough between'threads.

' By reason of the differences in curvature of 10 the different portionsof the thread, the threads A 4and B are not symmetrical with referenceto the base portion of the the diametrical pitch line P. In other. Wordsthe Apitch line does not bisect the thread contour.

In the modiiication lshown in Figs. 4 and 515 the trough between thethreads 3A of one member is filled out to form a flat surface 4beginning approximately at the bottom of the flattened bands 6' ofadjacent threads. 'Ihe crests 5 of the cooperating threads b of theother member are correspondingly attened.

As shown in Fig. 6, an annular washer 1 may be interposed between theend of the drill rod I and the bit 2. This washer serves to cushion ltheblows and accommodates any inaccuracies in. the shape ofthe end of thedrill rod and the end of the bore of the bit. f

The above described thread con/struction `does not bind or jam under themost severe usage. The threads are not battered out of shape and hencethe threads do not bind. The difference in curvature at the crest and atthe base of the threads permits compensation for difference in thestrength of the materials of which the drill lrod and bit are made.

What I claim is:

1. A separable drill bit construction comprising a threaded drill rodandan interiorly threaded bit thereon, the radius of curvature of the outer40 radius of curvature of the inner portions of said threads, therebygiving the thread a prole diiferent from the profile of the spacebetween threads and the thread of one member conformmember. 2. Aseparable drill bit construction comprising a threaded drill rod and aninteriorly threaded bit thereon, the radius of lcurvature of th outer ofsaid thread' and the thread of said bit being shaped to vconform to thespace between threads of said rod. I

JOHN B. BAKER..

